The present invention relates to the area of in-ground non-hydraulic automotive lift systems.
At about the time of the advent of in-ground hydraulic automotive lift systems, the introduction of which occurred in about the year 1920, certain limited efforts were made to create non-hydraulic automotive lift employing a thrust screw in combination with a load not mounted thereon. Examples known to the inventor of these efforts are reflected in U.S. Pat. No. 1,585,596 (1926) to Menges and U.S. Pat. No. 1,650,438 (1927) to Gass. Notwithstanding such early experimentation at about the time of the initial development of the in-ground hydraulic lift, most later efforts in connection with automotive screw lifts related to above ground systems of the type reflected in U.S. Pat. No. 3,602,338 (1971) to Sherry. However, for the most part, the use of screw lift systems in the automotive area have been limited to jack-type devices for use above ground and with relatively light vehicles, as is reflected in U.S. Pat. No. 3,532,322 (1970) to Webster.
It is noted that, in non-automotive areas, such as the elevator lift art, various screw drive mechanism have been proposed, as, for example, is shown in U.S. Pat. No. 3,468,401 (1969) to Letz.
The impetus, at this time, to the development of an in-ground automotive non-hydraulic automotive lift has come about through the realization:that in-ground hydraulic lifts, utilizing as they do hundreds of gallons of hydraulic fluid per year, give rise to an environmental hazard of proportions which are only now becoming apparent. More particularly, hydraulic fluid, while for the most part comprising an oil-based hydrocarbon carbohydrate, includes certain caustic and heavy metal additives including iron, lead, copper, tin, aluminum, nickel, phosphorus, molybdenum and cadmium. These additives, if permitted to penetrate the water table, can give rise to contamination of the water supply at concentrations of only a few parts per billion. There is, thereby, a burgeoning awareness on the part of environmental officials and others that the in-ground hydraulic lift, which has been a standard in service stations throughout the world since 1920, presents an actual and/or potential health hazard of still unmeasured magnitude.
The above problem, as may be appreciated, is more acute in areas where the water table is very high, such as in coastal areas of Florida and Louisiana where the water table can be as high as three feet below the surface. Thereby, the typical prior art in-ground hydraulic lift, which is installed to a depth of about nine feet in the ground, presents a particularly serious hazard in such areas. Further, the state-of-the-art of monitoring, typically being such means as microwave and electronic systems, the extent, location, and form of ground pollution has made it more feasible to conduct environmental surveys of virtually any business or industrial site for purposes of location of pollution, whether occurring as a result of system leakage or otherwise.
The instant invention may, thereby, be viewed as a response to the recognition of the environmental hazards associated with in-ground hydraulic technology.
Another difficulty in the prior art of hydraulic in-ground lifts is that the hydraulic cylinder of a rear piston assembly thereof is typically encased in at least three inches of concrete to comply with prevailing regulatory requirements. Notwithstanding such concrete encasement, the entire rear hydraulic assembly casing is, over time, susceptible to corrosion and therefore leakage. The economic consequences thereof are major disaster to a typical service station in that, to remedy such a problem, it is necessary to saw cut and jackhammer the floor of the service station to reach the bottom of the casing. This is a costly procedure which, as a further negative, renders the service station essentially unusable for a the period of at least days. In terms of cost, such a repair operation can entail expenses on the order of tens of thousands of dollars.
It is therefore in response to such potentially ruinous economic, and as yet still unmeasured environmental, consequences of seventy-five years of in-ground hydraulic lift usage that the instant invention is directed.